Microelectromechanical Systems from Aligned Cellulose Nanocrystal Films

Abstract

Microelectromechanical systems (MEMS) have become a ubiquitous part of a multitude of industries including transportation, communication, medical, and consumer products. The majority of commercial MEMS devices are produced from silicon using energy-intensive and harsh chemical processing. We report that actuatable standard MEMS devices such as cantilever beam arrays, doubly clamped beams, residual strain testers, and mechanical strength testers can be produced via low-temperature fabrication of shear-aligned cellulose nanocrystal (CNC) films. The devices had feature sizes as small as 6 μm and anisotropic mechanical properties. For 4 μm thick doubly clamped beams with the CNC aligned parallel to the devices' long axes, the Young's moduli averaged 51 GPa and the fracture strength averaged 1.1 GPa. These mechanical properties are within one-third of typical values for polysilicon devices. This new paradigm of producing MEMS devices from CNC extracted from waste biomass provides the simplicity and tunability of fluid-phase processing while enabling anisotropic mechanical properties on the order of those obtained in standard silicon MEMS.

Functional Materials from Nanocellulose: Utilizing Structure–Property Relationships in Bottom‐Up Fabrication

“…[ 49 ] Recent work in the Davis lab has demonstrated the preparation of microelectromechanical systems (MEMS) from shear‐casted aligned CNC films. [ 50 ] The resulting MEMS demonstrated both anisotropic mechanical and optical properties, which were tuned by controlling the direction of CNC alignment with respect to the long axis of the MEMS device. [ 50 ] Similarly, the MacLachlan lab has demonstrated the preparation of chemically crosslinked composites with uniaxially aligned CNCs via shearing of the precursor suspension between glass slides and subsequent photo‐ or thermal‐initiated polymerization.…”

“…[ 50 ] The resulting MEMS demonstrated both anisotropic mechanical and optical properties, which were tuned by controlling the direction of CNC alignment with respect to the long axis of the MEMS device. [ 50 ] Similarly, the MacLachlan lab has demonstrated the preparation of chemically crosslinked composites with uniaxially aligned CNCs via shearing of the precursor suspension between glass slides and subsequent photo‐ or thermal‐initiated polymerization. [ 51,52 ] These sheared composites show ionic strength‐dependent anisotropic swelling profiles, whereby an increase in ionic strength leads to significantly higher shrinking in the direction perpendicular to CNC alignment, and a corresponding increase in the overall birefringence of the hydrogel; a phenomenon which could be useful in sensing applications.…”

Recent Progress in Cellulose Nanocrystal Alignment and Its Applications

“…The resulting device structures had fracture sizes of 6 μm. 167 These kinds of MEMS (Figure 13) will find immense applications including medical, transportation, and communication products. Wet spun fibers were developed by mixing sodium alginate solution with CNCs.…”

Bottom-up assembly of nanocellulose structures

“…CNC films with tunable long-range order have been proposed as templates in the formation of chiral, mesoporous materials, which can be implemented in antireflective coatings, plasmonic and photonic devices (Giese et al, 2015). Additionally, aligned supported CNC films have also been implemented in the development of bio-based microelectromechanical systems (MEMS), which are used in, for example, the medical, communication and transportation industries (Saha et al, 2018). It has also been speculated, that combined with the piezoelectric properties of nanocellulose films (Rajala et al, 2016), CNC MEMS could be used in actuation and sensing applications (Saha et al, 2018).…”

“…Additionally, aligned supported CNC films have also been implemented in the development of bio-based microelectromechanical systems (MEMS), which are used in, for example, the medical, communication and transportation industries (Saha et al, 2018). It has also been speculated, that combined with the piezoelectric properties of nanocellulose films (Rajala et al, 2016), CNC MEMS could be used in actuation and sensing applications (Saha et al, 2018).…”